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Left Ventricular Assist Device

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khaled subeh

on 6 May 2015

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Transcript of Left Ventricular Assist Device

Introduction
Computational Flow Dynamics Studies
Any
Questions

Clinical Trials of Pulsatile and Continuous LVADs
(LVAD)
Left Ventricular Assist Device
The Heart
Heart is the strongest muscle in the human's body which provides the blood to all body organs.
Heart Consists of four chambers:
i. Right Atrium. ii. Right Ventricle.
iii. Left Atrium. iv. Left Ventricle.
Heart Failure (HF)
Heart failure

is a
chronic
,
progressive condition
in which the heart muscle is
unable to pump enough blood
through the heart
to meet the body's needs
for blood and oxygen.
Heart failure usually results in an
enlarged heart.
http://en.wikipedia.org/wiki/Pulmonary_valve#mediaviewer/File:Diagram_of_the_human_heart_(cropped).svg
Hypertension
is the most contributing factor to HF.
Types of heart failure
1. Left-sided HF (LV)
2. Right-sided HF (RV)
Left-sided (LV) heart failure is more common than Right-sided (RV) heart failure.
There are two types of LVHF:
I.
Systolic Failure
II.
Diastolic Failure
There is a
weakness
in
contraction
of
left ventricle.
Anas - Emad - Ameen - Amani
Mahmoud

By:
Supervisor: Dr. Othman Al-Smadi
Also called "
Diastolic Dysfunction
"
During the
relaxation
, the heart can not fill with enough blood.
When the left ventricle fails, the fluid's pressure will increase, that will cause those fluids to be transferred back through the lungs.
Treatments of Heart Failure
lifestyle Changes.
Medications.
Surgical Procedures.
Implantable medical devices
Implantable medical devices
1. Valve Replacement
The heart has
4 valves:
The mitral valve
and
tricuspid valve
, which control blood flow from the atria to the ventricles.
The aortic valve
and
pulmonary valve
, which control blood flow out of the ventricles.
We can replace those valves with:
1. Mechanical Valves
made of metal and plastic.
2
. Valves of
another human
or
animal tissue.
2. Defibrillator Implantation
When those valves
do not work properly
, this will leads to HF.
.Used for patients who have
severe heart failure.
The Defibrillators are
surgically placed
and deliver pacing to the heart.
Implantable medical devices
3. Heart Assistance Devices
Heart assistance devices are called
Ventricular Assist Device (VAD)
There are two types of VAD:
1. Right Ventricular assist device
(RVAD):
They are used only in short-term support for RV.
It pumps the de-oxygenated blood from RV to Pulmonary artery .
2. Left Ventricular assist device
(LVAD):
LVAD is the most common assist device used.
It pumps the oxygenated blood from LV to Aorta .
The treatment with LVAD is the best method to improve in the patient life.

http://watchlearnlive.heart.org/media/hrtflr-01
The left Ventricular assist device
LVAD
is a
mechanical pump
used as therapy for patients with HF.

We use the LVAD
until the patient can receive a heart transplant.

2. Bridge-to-Recovery.
We use the LVAD until
the patient's heart recovers then the device can be explanted.

3. Destination Therapy.
We use the LVAD
for long-term, permanent support in patients who are not candidates for a heart transplant.
The left Ventricular assist device
There are
two technologies
used in
the pumping system
in LVADs:
1. Pulsatile Flow Pumps
(PFP).
Undar
has declared that
pulsatile flow
may be quantified in terms of
energy equivalent pressure (EEP).
PFP
mimics the natural pulsing action
of the heart.
EEP
is the ratio between the area under the curve of power and the area under the curve of flow at the end of the cardiac cycle.
Pulsatile Flow Pumps (PFP)
The pulsatile pump's components are shown in the figure below:


http://rebelem.com/wp-content/uploads/2014/05/Pulsatile-Flow-LVAD
LVADs are used for
3 classes of therapy.
1. Bridge-to-Transplant.
The left Ventricular assist device
2. Continuous Flow Pumps
(CFP).
It does
not
depend on
the cardiac pressure
(systolic and diastolic)
This type of flow is called
"non-pulsatile"
.
Continuous flow are smaller and have proven to be
more durable
than pulsatile.
They normally use either
a centrifugal pump
or
an axial flow pump.
Both types have
a central rotor
containing
permanent magnets
Controlled electric currents
running through
coils
contained in
the pump housing
apply
forces
to
the magnets
, which in turn cause
the rotors to spin
.
Fukamachi, Kiyo; Smedira, Nicholas (August 2005). "Smaller, Safer, Totally Implantable LVADs: Fact or Fantasy?". American College of Cardiology Current Journal Review 14 (8): 40–42.
Continuous Flow Pumps (CFP)
The continuous pump's components are shown in the figure below:


http://rebelem.com/wp-content/uploads/2014/05/Continuous-Flow-LVAD
Pulsatile or Continuous?
At the
American Heart Association (AHA)
meeting
2009,
it was reported by the press media that a
new type of device
more than doubles
the two-year survival rate
among heart failure patients.
The new device, called
HeartMate II,
improves survival, is more
durable
, and is
linked to better quality of life
.
The device works by

pumping blood continuously
rather than simulating a heart beat as older pumps do.

The pump is
connected to equipment outside the body
– a
small computer
and
batteries
that the patient
wears in a belt pack
using a wire from the patient's abdomen.
The
FDA
has approved the device only as a temporary
bridge to transplant.
HeartMate II Study
The goal of the study was to compare treatment with
a continuous-flow
HeartMate II LVAD compared with a
pulsatile-flow
HeartMate XVE LVAD among patients with advanced heart failure
not eligible
for
heart transplantation.
HeartMate II study was a
randomized tria
l
that enrolled patients in a
2:1 ratio
.
Continuous-flow device
(n=134)
and pulsatile-flow device
(n=66)
In the continuous-flow group,
the mean age
was
62 years
,
19% were women
,
66%
had
ischaemia
as
the cause of heart failure
, and the
mean cardiac index
was
2.0 L/min/m2
.
HeartMate II Study
The primary endpoint
was
survival at two years
without
disabling stroke
or
reoperation to
repair/replace
the device.
Secondary endpoints
included
functional status
,
quality of life
, and
frequency of adverse events.
The Study Endpoints
The primary outcome
(survival free from stroke or reoperation to repair/replace the assist device)
46%
(62/134)
in the
continuous-flow
group vs. 11%
(7/66)
in the
pulsatile-flow
group.
Disabling stroke
was
11%
vs.
12%
Reoperation to repair/replace
the assist device was
10% vs. 36%

Death
within
two years
was
33%
vs.
41%

Rehospitalisation
was reduced by
38%
with the
continuous-flow device.
Functional class I or II
at
12 months
was
76%
vs.
61%
The secondary outcome
HeartMate II Study
It was concluded that
a continuous-flow LVAD
significantly improved the probability of
survival free from stroke
and
device failure
at
two years
compared with
a pulsatile device.
There was
an improvement
in
survival at two years
for the continuous-flow vs. the pulsatile-flow LVAD.
Both devices significantly
improved the quality of life
and
functional capacity.
The
smaller pump
and
percutaneous lead
in the c
ontinuous-flow LVAD
requires
less surgical dissection
for
implantation
which
reduces the potential for infection.
mate fot the heart: Pulsatile or Continuous?
Neth Heart J. Feb 2010; 18(2): 59.
Hemodynamic of Pulsatile
Flow Pumps
Pulsatile LVADs
are good
in case of patients with
severe heart failure.
One of the important
hemodynamic
properties is
hemolysis
which occurs due to
high sheer rate
and
turbulence.

Hemolysis usually associated with
valve closure
.
Hemodynamic of Continuous
Flow Pumps
Continuous LVADs are good hemodynamic support
without causing hemolysis
. But even though the
hemolysis is infrequent
.
Other disorders occurred such as
platelet dysfunction.
The formation of
thrombosis
and
hemolysis
vary
depending on the type of CFP
.
Problems occur while using LVADs
Problems of pulsatile LVAD
Adverse events
while using pulsatile LVADs can be devided into:
a)
Device-related adverse events:
Infection may occur
due to the percutaneous lead, pump, or pump pocket .
b)
Non device-related adverse events.
These events can be summarized as
right heart failure
,
respiratory failure
,
renal failure
and
cardiac arrhythmia.
Problems occur while using LVADs
Problems of continuous LVAD
a)
Bleeding complications and thromboembolic events :
b)
Obstruction:
This is the most serious adverse event in continuous LVAD patients.
It is occurred to inflow or outflow cannula when blocked or kinked duo to high pressure difference across the pump.
Flow obstruction will limit pump flow.
c)
Suction Events :
It occurs when the pump speed is set higher than appropriate.
Theoretical assumptions used in the experiment
Parameter Values to stimulate different degrees of Hear Failure
Comparison between the outflow of native heart and outflow of LVAD
To
simulate native heart pulsatile flow
, they used
a silicon model of aorta
and connected to a
MEDOS ventricle.
This is called
MRI compatible mock loop circuit.
LVAD outflow cannula was stated in
3 different positions
(B: 45˚ ascending aorta, C: 90˚ ascending aorta, D: Descending aorta)
Comparison between the outflow of native heart and outflow of LVAD
3D visualization of the four different models (A-D) during systole and diastole.
Comparison between the hemodynamic properties due to insertion the cannula of the LVAD in the ascending aorta and descending aorta.
Streamlines of
the cycle-averaged flow
in the
thoracic aorta
and
the ventricular assist device (VAD) graft tube
with outflow graft anastomosis to the descending aorta
(A, B)
versus the ascending aorta
(C, D)
in a
2-dimensional computer model.
The total output
(cardiac plus VAD)
is
4 L/min
In
A
and
C,

75%
of the output occurs through the
VAD
; in
B
and
D, 100%
of the output is through the VAD (the aortic valve remains closed).
A study by
CristophBenk et al.
(2012)
, which
analyzed
blood flow patterns
in aorta
with and without LVAD support,
and the effect of different positions of LVAD
outflow cannula
in blood flow using flow sensitive
4D MRI.
Methodology
To investigate the
different influences
due to using
pulsatile flow left ventricle assist devices
and
continuous flow left ventricle assist devices
, a
3-dimensional model
of the aortic artery will be used in the study .
The model consisted of
a curved channel
that
represented the ascending aorta
,
aortic arch
, and
descending aorta.
A pulsatile flow rate and continuous flow rate .
The waveforms of both continuous and pulsatile velocity profiles are shown
?
Parameter Values to Simulate degrees of
heart failure
Comparison between the hemodynamic properties due to insertion the cannula of the LVAD in the ascending aorta and descending aorta.
The
LVAD
can be implanted either through a
midline sternotomy
with the
anastomosis
to

the ascending aorta
or through
a left thoracotomy
with the
outflow–graft anastomosis
to the
descending thoracic aorta.
Each technique of the mentioned
techniques
has its
advantages
and
disadvantages.
Biswajit and associate (2005)
described
a computer generated flow-model
that
illustrated the flow dynamics
and
possible clinical consequences of each method
.
Comparison between the hemodynamic properties due to insertion the cannula of the LVAD in the ascending aorta and descending aorta.
Their simulation showed that when
a descending aortic anastomosis
is used, there is a
net back flow
in
the descending aorta
to
supply the carotid
and
subclavian arteries.

Due to this
reverse flow
in the aorta , the
flow velocity
become
almost zero

in a large region of the ascending aorta
.
Where a
stagnant flow
was detected over many cycles, a similar flow in the aorta could lead to
thrombogenesis.
However ,there was
no stagnant flow
in the use of
an ascending aortic outflow graft anastomosis.
Full transcript